He's accused of having a 'hidden agenda'. [=a secret plan]
His suggestions have a 'hidden' [='secret'] purpose.
There was a 'hidden' flaw in the airplane's design.
(..) Dialogue: Marked=..,Default,NTP,!Effect,...that was drinking its blood,\Nthat was Voldemort? Dialogue: Marked=..,Default,NTP,!Effect,Do you know what is hidden\Nin the school at this very moment, Mr. Potter? Dialogue: Marked=..,Default,NTP,!Effect,The Sorcerer's Stone. (..)2001 Harry Potter and the Sorcerer's Stone